/*
 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 */

package java.awt;

import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.awt.geom.AffineTransform;
import java.awt.image.ColorModel;
import java.beans.ConstructorProperties;

/**
 * The <code>GradientPaint</code> class provides a way to fill
 * a {@link Shape} with a linear color gradient pattern.
 * If {@link Point} P1 with {@link Color} C1 and <code>Point</code> P2 with
 * <code>Color</code> C2 are specified in user space, the
 * <code>Color</code> on the P1, P2 connecting line is proportionally
 * changed from C1 to C2.  Any point P not on the extended P1, P2
 * connecting line has the color of the point P' that is the perpendicular
 * projection of P on the extended P1, P2 connecting line.
 * Points on the extended line outside of the P1, P2 segment can be colored
 * in one of two ways.
 * <ul>
 * <li>
 * If the gradient is cyclic then the points on the extended P1, P2
 * connecting line cycle back and forth between the colors C1 and C2.
 * <li>
 * If the gradient is acyclic then points on the P1 side of the segment
 * have the constant <code>Color</code> C1 while points on the P2 side
 * have the constant <code>Color</code> C2.
 * </ul>
 *
 * @version 10 Feb 1997
 * @see Paint
 * @see Graphics2D#setPaint
 */

public class GradientPaint implements Paint {

  Point2D.Float p1;
  Point2D.Float p2;
  Color color1;
  Color color2;
  boolean cyclic;

  /**
   * Constructs a simple acyclic <code>GradientPaint</code> object.
   *
   * @param x1 x coordinate of the first specified <code>Point</code> in user space
   * @param y1 y coordinate of the first specified <code>Point</code> in user space
   * @param color1 <code>Color</code> at the first specified <code>Point</code>
   * @param x2 x coordinate of the second specified <code>Point</code> in user space
   * @param y2 y coordinate of the second specified <code>Point</code> in user space
   * @param color2 <code>Color</code> at the second specified <code>Point</code>
   * @throws NullPointerException if either one of colors is null
   */
  public GradientPaint(float x1,
      float y1,
      Color color1,
      float x2,
      float y2,
      Color color2) {
    if ((color1 == null) || (color2 == null)) {
      throw new NullPointerException("Colors cannot be null");
    }

    p1 = new Point2D.Float(x1, y1);
    p2 = new Point2D.Float(x2, y2);
    this.color1 = color1;
    this.color2 = color2;
  }

  /**
   * Constructs a simple acyclic <code>GradientPaint</code> object.
   *
   * @param pt1 the first specified <code>Point</code> in user space
   * @param color1 <code>Color</code> at the first specified <code>Point</code>
   * @param pt2 the second specified <code>Point</code> in user space
   * @param color2 <code>Color</code> at the second specified <code>Point</code>
   * @throws NullPointerException if either one of colors or points is null
   */
  public GradientPaint(Point2D pt1,
      Color color1,
      Point2D pt2,
      Color color2) {
    if ((color1 == null) || (color2 == null) ||
        (pt1 == null) || (pt2 == null)) {
      throw new NullPointerException("Colors and points should be non-null");
    }

    p1 = new Point2D.Float((float) pt1.getX(), (float) pt1.getY());
    p2 = new Point2D.Float((float) pt2.getX(), (float) pt2.getY());
    this.color1 = color1;
    this.color2 = color2;
  }

  /**
   * Constructs either a cyclic or acyclic <code>GradientPaint</code>
   * object depending on the <code>boolean</code> parameter.
   *
   * @param x1 x coordinate of the first specified <code>Point</code> in user space
   * @param y1 y coordinate of the first specified <code>Point</code> in user space
   * @param color1 <code>Color</code> at the first specified <code>Point</code>
   * @param x2 x coordinate of the second specified <code>Point</code> in user space
   * @param y2 y coordinate of the second specified <code>Point</code> in user space
   * @param color2 <code>Color</code> at the second specified <code>Point</code>
   * @param cyclic <code>true</code> if the gradient pattern should cycle repeatedly between the two
   * colors; <code>false</code> otherwise
   */
  public GradientPaint(float x1,
      float y1,
      Color color1,
      float x2,
      float y2,
      Color color2,
      boolean cyclic) {
    this(x1, y1, color1, x2, y2, color2);
    this.cyclic = cyclic;
  }

  /**
   * Constructs either a cyclic or acyclic <code>GradientPaint</code>
   * object depending on the <code>boolean</code> parameter.
   *
   * @param pt1 the first specified <code>Point</code> in user space
   * @param color1 <code>Color</code> at the first specified <code>Point</code>
   * @param pt2 the second specified <code>Point</code> in user space
   * @param color2 <code>Color</code> at the second specified <code>Point</code>
   * @param cyclic <code>true</code> if the gradient pattern should cycle repeatedly between the two
   * colors; <code>false</code> otherwise
   * @throws NullPointerException if either one of colors or points is null
   */
  @ConstructorProperties({"point1", "color1", "point2", "color2", "cyclic"})
  public GradientPaint(Point2D pt1,
      Color color1,
      Point2D pt2,
      Color color2,
      boolean cyclic) {
    this(pt1, color1, pt2, color2);
    this.cyclic = cyclic;
  }

  /**
   * Returns a copy of the point P1 that anchors the first color.
   *
   * @return a {@link Point2D} object that is a copy of the point that anchors the first color of
   * this <code>GradientPaint</code>.
   */
  public Point2D getPoint1() {
    return new Point2D.Float(p1.x, p1.y);
  }

  /**
   * Returns the color C1 anchored by the point P1.
   *
   * @return a <code>Color</code> object that is the color anchored by P1.
   */
  public Color getColor1() {
    return color1;
  }

  /**
   * Returns a copy of the point P2 which anchors the second color.
   *
   * @return a {@link Point2D} object that is a copy of the point that anchors the second color of
   * this <code>GradientPaint</code>.
   */
  public Point2D getPoint2() {
    return new Point2D.Float(p2.x, p2.y);
  }

  /**
   * Returns the color C2 anchored by the point P2.
   *
   * @return a <code>Color</code> object that is the color anchored by P2.
   */
  public Color getColor2() {
    return color2;
  }

  /**
   * Returns <code>true</code> if the gradient cycles repeatedly
   * between the two colors C1 and C2.
   *
   * @return <code>true</code> if the gradient cycles repeatedly between the two colors;
   * <code>false</code> otherwise.
   */
  public boolean isCyclic() {
    return cyclic;
  }

  /**
   * Creates and returns a {@link PaintContext} used to
   * generate a linear color gradient pattern.
   * See the {@link Paint#createContext specification} of the
   * method in the {@link Paint} interface for information
   * on null parameter handling.
   *
   * @param cm the preferred {@link ColorModel} which represents the most convenient format for the
   * caller to receive the pixel data, or {@code null} if there is no preference.
   * @param deviceBounds the device space bounding box of the graphics primitive being rendered.
   * @param userBounds the user space bounding box of the graphics primitive being rendered.
   * @param xform the {@link AffineTransform} from user space into device space.
   * @param hints the set of hints that the context object can use to choose between rendering
   * alternatives.
   * @return the {@code PaintContext} for generating color patterns.
   * @see Paint
   * @see PaintContext
   * @see ColorModel
   * @see Rectangle
   * @see Rectangle2D
   * @see AffineTransform
   * @see RenderingHints
   */
  public PaintContext createContext(ColorModel cm,
      Rectangle deviceBounds,
      Rectangle2D userBounds,
      AffineTransform xform,
      RenderingHints hints) {

    return new GradientPaintContext(cm, p1, p2, xform,
        color1, color2, cyclic);
  }

  /**
   * Returns the transparency mode for this <code>GradientPaint</code>.
   *
   * @return an integer value representing this <code>GradientPaint</code> object's transparency
   * mode.
   * @see Transparency
   */
  public int getTransparency() {
    int a1 = color1.getAlpha();
    int a2 = color2.getAlpha();
    return (((a1 & a2) == 0xff) ? OPAQUE : TRANSLUCENT);
  }

}
